It is known to produce containers, such as plastics bottles and similar, from preforms which are formed into the containers in a molding cavity of a mold by injecting a gaseous or liquid forming fluid in the preforms.
The preforms are placed in successive molds and the injection is performed at a container forming station comprising a wheel, or carousel, movable in rotation and carrying the molds. The injection is performed at a high pressure via an injection nozzle which is placed over the neck, or introduced in the neck, of the preforms.
However, the high pressure of the injection can deform the neck of the preforms, which then forms a container of poor quality, which has to be rejected. The number of unsatisfactory containers due to neck deformation reduces the throughput of the machine.
In the case of a liquid forming fluid, the liquid intended to fill the container is directly injected in the preform at the container forming station and participates to the forming of the container. The container containing the liquid is then moved at high speed to the closing station where a lid or a cap is applied to the container. This forming method is known as hydraulic forming.
The containers are transported at high speed while containing liquid. More particularly, the containers containing liquid are moved in rotation, which generates an important centrifugal force on the containers. This centrifugal force, and more generally transporting the containers at high speed, can lead to spilling the liquid contained in the containers. When the molds are in mold holders, arranged to close and lock the molds, the spilled liquid will soil the mold and the mold holder. However, the mold holder is hard to clean due to its complicated structure, and cleaning the mold holder implies stopping the rotation of the wheel and therefore reduces the throughput of the forming station. An insufficient cleaning of the molds and mold holders can lead to cross-contamination in the hydraulic forming method. Consequently, the speed of rotation of the wheel is necessarily limited in order to avoid the above-mentioned problems.
WO-2013/020885 discloses a machine and a method for forming and filling containers using a liquid. In this machine, the longitudinal axes of the forming stations are inclined at 45° relative to the vertical axis of rotation of the forming stations. This document explains that this inclination makes it possible to avoid splashing and spilling of the liquid due to the centrifugal force exerted on the liquid in motion.
However, such a machine has a complicated structure and can lead to difficulties for placing the preforms in the molds and for retrieving the formed and filled containers from the molds.
Consequently, an alternative method for preventing spilling of liquid is needed.
DE-195 47 425 discloses a method for forming containers, wherein a device is attached to the neck of a preform to guide a forming gaz inside the preform during forming of the container from the preform. However, this document does not mention the problem of preventing the spilling of the liquid once the container has been filled and does not disclose a solution to this problem. US-2012/0187133 also does not disclose this problem and an appropriate solution to it.
One of the aims of the invention is to overcome the drawbacks mentioned above, by proposing a device able to prevent the deformation of the neck of the preforms during injection and to limit the risks of spilling the liquid contained in the formed containers.